C HAPTER 4: C ARBON C HEMISTRY Organic chemistry studies carbon compounds; the backbone of biological macromolecules When C forms four covalent bonds, its hybrid orbitals create a tetrahedral shape. When 2 C’s are joined by a double bond, a flat molecule forms Figure 4.1

The electron configuration of carbon gives it covalent compatibility with many different elements. What are some possibilities of molecules or compounds that could form with the following molecules? H O NC Hydrogen (valence = 1) Oxygen (valence = 2) Nitrogen (valence = 3) Carbon (valence = 4) Figure 4.4

C ARBON B ONDING Carbons readily bond with each other; they form single, double, triple, or quadruple bonds (a) Methane (b) Ethane (c) Ethene (ethylene) Molecular Formula Structural Formula Ball-and- Stick Model Space- Filling Model H H H H H H H H H H HH H H C C C CC CH 4 C2H6C2H6 C2H4C2H4 Name and Comments Figure 4.3 A-C

I SOMERS Isomers: compounds with same molecular formula but different structures & properties 1. Structural: differ in covalent arrangements of atoms or double bond locations 2. Geometric (stereoisomers): differ in spatial arrangements; have cis and trans arrangements 3. Enantiomers: mirror-image molecules H H HH H H H H HH H H H HH H H H H H H H H H H H H H CO 2 H CH 3 NH 2 C CO 2 H H CH 3 NH 2 XX X X C CCCC C C C CC C C C C C (a) Structural isomers (b) Geometric isomers (c) Enantiomers H Figure 4.7 A-C

M ORE ON G EOMETRIC I SOMERS Cis isomer: has non-hydrogen atoms attached to double bonded carbons on the same side of the double bond. Trans isomer has these atoms on opposite sides of the double bond.

T HALIDOMIDE : -- CONTAINS BOTH LEFT - AND RIGHT - HANDED ISOMERS IN EQUAL AMOUNTS. --T HE ( R ) ENANTIOMER IS EFFECTIVE AGAINST MORNING SICKNESS. T HE ( S ) CAUSES BIRTH DEFECTS. --T HE ENANTIOMERS CAN INTERCONVERT ISOMERS ENANTIOMER

Enantiomers : L-Dopa is a drug used to treat Parkinson’s…the drug’s enantiomer has no effect on patients. L-Dopa (effective against Parkinson’s disease) D-Dopa (biologically inactive) Figure 4.8

F UNCTIONAL G ROUPS Functional groups are the parts of molecules involved in chemical reactions They are the chemically reactive groups of atoms within an organic molecule Give organic molecules distinctive chemical properties CH 3 OH HO O CH 3 OH Estradiol Testosterone Female lion Male lion Figure 4.9

Six functional groups are important in the chemistry of life Hydroxyl Carbonyl Carboxyl Amino Sulfhydryl Phosphate Study and Learn Figure 4.10 in your text

Some important functional groups of organic compounds STRUCTURE (may be written HO ) HYDROXYL CARBONYL CARBOXYL OH A hydrogen atom is bonds to an oxygen atom, which in turn is bonded to the carbon skeleton of the organic molecule. (Do not confuse this functional group with the hydroxide ion, OH –.) When an oxygen atom is double-bonded to a carbon atom that is also bonded to a hydroxyl group, the entire assembly of atoms is called a carboxyl group (—COOH). C OO C OH Figure 4.10 The carbonyl group ( CO) consists of a carbon atom joined to an oxygen atom by a double bond. 

S OME IMPORTANT FUNCTIONAL GROUPS OF ORGANIC COMPOUNDS Acetic acid, which gives vinegar its sour taste NAME OF COMPOUNDS Alcohols (their specific names usually end in -ol) Ketones if the carbonyl group is within a carbon skeleton Aldehyde s if the carbonyl group is at the end of the carbon skeleton Carboxylic acids, or organic acids EXAMPLE Propanal, an aldehyde Acetone, the simplest ketone Ethanol, the alcohol present in alcoholic beverages H H H HH CC OH H H H H H H H C C H C C C CCC O H O H H HH H O H Figure 4.10

Some important functional groups of organic compounds The amino group (—NH 2 ) consists of a nitrogen atom bonded to two hydrogen atoms and to the carbon skeleton. AMINO SULFHYDRYL PHOSPHATE (may be written HS ) The sulfhydryl group: a sulfur atom bonded to a hydrogen; resembles a hydroxyl group in shape. In a phosphate group, a phosphorus atom is bonded to four oxygen atoms; one oxygen is bonded to the carbon skeleton; two oxygens carry negative charges; abbreviated P. N H H SH O P O OH Figure 4.10